1. Field of the Invention
The present invention relates to heat sinks, and particularly to a heat sink having high density fins in which the fins are firmly combined together.
2. Prior Art
Advances in microelectronics technology have resulted in electronic devices which process signals and data at unprecedented high speeds. During operation of many contemporary electronic devices such as central processing units (CPUs), large amounts of heat are produced. The heat must be efficiently removed, to prevent the system from becoming unstable or being damaged. Heat sinks are frequently used to dissipate heat from these electronic devices.
Contemporary CPUs are also being made smaller than previously. Thus a modern CPU can generate a huge amount of heat in a relatively small volume. A typical heat sink is integrally made by extruding aluminum. The heat sink has a base, and a plurality of spaced, parallel fins extending upwardly from the base. However, the width-to-height ratio of the heat sink is limited by the extrusion process. Thus, the effective heat-dissipating area of the heat sink is restricted.
In order to overcome the limitations of extrusion, a folded-fin structure for a heat sink has been devised. The folded-fin structure is integrally concertinaed, and is made by bending a single metal sheet. This kind of heat sink has no limitations on the width-to-height ratio of the fins. For example, Taiwan Pat. No. 390459 discloses a heat sink with folded fins. However, a total contact area between the fins and a heat conductive base of the heat sink is only half of an area of the base. Because the contact area is limited, transfer of heat from the base to the fins is correspondingly limited.
In order to overcome the above-described contact area problem, another kind of heat sink has been devised. The heat sink includes a plurality of stacked fins. Each fin is separately formed. The fins are then stacked together, and attached onto a base. This kind of heat sink provides a much larger contact area between the fins and a heat conductive base. For example, China Pat. No. 00209935.7 discloses combined heat sink fins. Each fin forms two flanges at upper and lower ends thereof. A plurality of tabs and a plurality of cutouts are formed at each flange of each fin. An indent portion is formed in each tab. The tabs of each fin are extended into corresponding cutouts of an adjacent fin. The indent portions prevent the tabs from escaping from the cutouts. All the fins are thereby combined together.
However, the combined fins are relatively loose, because the fins are combined together only by way of the tabs extending into cutouts. The combined fins are easily deformed, and difficult to keep intact during transportation or assembly. In addition, combining points of the fins are located at lower and upper ends of the fins, which creates an uneven contacting surface between the combined fins and a heat-conductive base. The uneven contacting surface comprises a plurality of recessed portions, and lowers the heat transfer efficiency of the heat sink.
An improved heat sink with combined fins which overcomes the above-mentioned problems is desired.